Musnad Ahmad 33:272

Abu Mu'awiyah narrated to us, Al-A'mash narrated to us, from Abu Sufyan, from Jabir, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "There is no male or female except that upon his head is a rope tied with three knots when he sleeps. If he wakes up and remembers Allah, a knot is untied. If he gets up and performs ablution, a knot is untied. If he stands for prayer, all of his knots are untied."